The first line in the input file (after concatenation of multiple input files), and the first line following a /newjob line, is considered a title line and is not parsed but kept as the name of the circuit. The exceptions to this rule are old format margin analysis input files and Xic files.
Command lines must be surrounded by the lines .exec or .control and .endc in the file, or prefixed by ``*@'' or ``*#'' in order to be recognized as commands, except in startup files where all lines but the title line are taken as executable. Commands found in .exec blocks or *@ lines are executed before the circuit is parsed, thus can set variables used in the circuit. Commands found in .control blocks or *# lines are executed after the circuit is parsed, so a control line of ``ac ...'' will work the same as the corresponding .ac line, for example. Use of the ``comment'' control prefixes *@ and *# makes it possible to embed commands in WRspice input files that will be ignored by earlier versions of SPICE.
Shell variables found in the circuit deck (but not in the commands text) are evaluated during the source. The reset command can be used to update these variables if they are later changed by the shell after sourcing.